The invention relates to transmissions, and more particularly to improvements in transmissions of the type wherein an endless flexible element (especially a chain) is trained over a plurality of rotary members in the form of pulleys or sheaves, wheels, gears or the like. Examples of transmissions of the type to which the present invention pertains are those known as infinitely or continuously variable transmissions (called CVTs) wherein an endless flexible belt, band or chain (herein-after called chain) is trained over adjustable pulleys or sheaves (hereinafter pulleys). Transmissions of such character are utilized in the power trains of numerous types of motor vehicles to transmit torque between a prime mover (such as an internal combustion engine or a hybrid employing a motor and an engine) and the axles of front and/or rear wheels, e.g., by way of a differential.
Continuously variable transmissions of the type to which the present invention pertains and which can be utilized in the power train of a motor vehicle are disclosed, for example, in German patent No. 42 34 294. Endless chains which can be utilized in such transmissions are disclosed in German patents Nos. 43 30 696 (this publication discloses a chain which is designed to transmit tractive or tensile force) and 26 43 528 (this publication describes endless chains designed for the transmission of thrust).
A continuously or infinitely variable transmission (hereinafter called transmission for short) of the type to which the present invention pertains is likely or bound to generate noise when in actual use. Such undesirable side effect is attributable primarily to at least one of the elongated portions (known as stretches or reaches) of an endless flexible chain which is trained over at least two rotary members. For example, a CVT normally employs first and second adjustable rotary pulleys which are rotatable about parallel axes. The chain is or can be a so-called link chain or pintle chain and includes a first arcuate portion having a variable radius of curvature and being trained over a first pulley, a second arcuate portion having a variable radius of curvature and being trained over a second pulley, a first elongated (e.g., substantially or exactly straight) reach or stretch extending between the two arcuate chain portions from one of the first and second pulleys to the other of these pulleys, and a second elongated reach or stretch extending between the two arcuate portions from the other to the one arcuate portion. The first stretch is acted upon by a pulling force when the second stretch is pushed, or vice versa, depending upon which of the pulleys is driven to transmit torque to the other pulley.
Noise is generated by at least one of the stretches of the chain as a result of transverse vibrations. Such vibrations are undesirable for numerous reasons. For example, if the vibrations are conveyed or communicated to the chassis of the motor vehicle, this can result in the generation of often readily detectable noise which is unpleasant to the driver as well as to other occupant(s) of the vehicle. Furthermore, vibrations cause extensive wear, e.g., upon the links and/or pintles and/or other constituents of the chain, i.e., they can unduly affect the useful life of the chain and of the entire transmission.
The disclosure of each U.S. and foreign patent and patent application identified in the specification of the present application is incorporated herein by reference. This also includes each priority application being relied upon by the present application.
An object of the present invention is to provide a transmission wherein an endless flexible element (such as a chain) is less likely to generate noise and/or to cause pronounced or excessive wear than the endless flexible elements in presently known continuously variable transmissions.
Another object of the invention is to provide a continuously variable transmission wherein the likelihood of noise generation is reduced in a simple, inexpensive and space-saving manner.
A further object of the invention is to provide a continuously variable transmission which exhibits the just outlined features, advantages and attributes and can be incorporated into the power trains of motor vehicles in a simple and time-saving manner.
An additional object of the invention is to provide a novel and improved chain and chain guide combination which can be incorporated into a continuously variable transmission of the above outlined character.
Still another object of the invention is to provide a power train which embodies a novel and improved continuously variable transmission or an analogous transmission.
A further object of the invention is to provide a novel and improved method of reducing the likelihood of noise generation by the chain or another endless flexible element of a transmission, such as a transmission wherein an endless flexible element is trained over at least two pulleys, gears, wheels or analogous rotary torque transmitting and/or torque receiving members.
Another object of the invention is to provide a transmission which is designed to generate less noise than conventional transmissions irrespective of whether one of the rotary members transmits torque to the other rotary member(s) or vice versa.
An additional object of the invention is to provide a novel and improved infinitely variable transmission of the type known as CVT, and to construct and assemble the transmission in such a way that it can be installed in existing power trains of or for motor vehicles as a superior substitute for existing transmissions of such character without necessitating any, or any appreciable, alterations under the hood of the motor vehicle.
Still another object of the invention is to provide a continuously variable or an analogous transmission the parts of which can be mass produced in available machines or production lines.
A further object of the invention is to provide a novel and improved guide for an endless flexible element which can be utilized in a transmission of the above outlined character.
Another object of the invention is to provide novel and improved means for supporting the guide in a continuously variable transmission or in the housing or casing of such transmission.
The invention is embodied in a transmission, such as a continuously variable transmission, which comprises a first rotary member (e.g., a first adjustable pulley wherein a first conical flange is movable axially toward and away from a second conical flange), a second rotary member (e.g., a second adjustable pulley similar to or identical with the first pulley and rotatable about an axis which is parallel to the axis of the first rotary member), and and endless flexible torque transmitting element (hereinafter called chain for short) having first and second arcuate portions respectively trained over the first and second rotary members, and first and second elongated stretches or reaches each of which extends between the first and second arcuate portions. In accordance with a feature of the present invention, the transmission further comprises an elongated guide for at least one stretch of the chain.
If the rotary members are adjustable pulleys, each thereof can be designed in such a way that one of its conical flanges is movable axially toward and away from but cannot rotate relative to the other conical flange. The arcuate portions of the chain contact the conical surfaces of the flanges forming part of the respective pulleys.
The guide can be provided with means for limiting the at least one stretch of the chain to movements along one or more paths of a plurality of predetermined paths each of which extends between the first and second portions of the chain. The exact path of the at least one stretch can vary continuously during adjustment of the rotary members if such rotary members constitute adjustable pulleys wherein one of the flanges is movable axially toward or away from the other flange.
The limiting means of the guide can define a short or an elongated channel adapted to receive a relatively short or a longer part of the at least one stretch of the chain.
The improved transmission can further comprise a holder or support and means for preferably movably mounting the guide on the suport. The mounting means can define a pivot axis for the guide, and such pivot axis is or can be parallel to the axes of the rotary members. Alternatively, or in addition to defining for the guide a pivot axis, the mounting means can be arranged to establish at least one path for lengthwise movements of the guide along such path.
The rotary members of the transmission are or can be spaced apart from each other, and the guide can be disposed or supported in the space between such rotary members.
It is also possible to provide the guide with at least one frame or to utilize a guide which constitutes a frame at least partially surrounding the at least one stretch of the chain.
It is also possible to utilize a composite guide or a one-piece guide having at least one portion exhibiting an at least substantially U-shaped outline and defining a channel which receives at least a portion of the at least one stretch of the chain.
Even though the guide at least partially surrounds (or can at least partially surround) the at least one stretch of the chain, such at least one stretch is or can be mounted with freedom of movement of the at least one stretch substantially radially of the parallel axes of the rotary members or at least substantially radially of the axis of at least one rotary member.
The guide can be provided with one or more projections in the form of strips, prongs, pins, tongues or the like. Each such projection can extend, at least in part, lengthwise of the at least one stretch of the chain.
In accordance with one presently preferred embodiment, the guide includes a central portion (such as a tunnel) which at least partially surrounds a median portion of the at least one stretch of the chain, and first and second projections which flank the central portion of the guide and respectively extend at least substantially lengthwise of the at least one stretch toward the first and second rotary members, i.e., toward the arcuate first and second portions of the chain.
The guide can include at least two projections which are disposed at opposite sides and extend at least substantially lengthwise of the at least one stretch; one of such at least two projections can be disposed at the inner side of the at least one stretch (i.e., the side which faces toward the axes of the rotary members), and the other projection can be disposed at the outer side of the at least one stretch.
The inner side of the at least one stretch of the chain confronts the normally parallel axes of the two rotary members, and the guide can include at least one projection which extends lengthwise of the at least one stretch at the inner or at the outer side of the at least one stretch.
The guide can be made of a single piece of a suitable metallic or plastic material or a combination of two or more different materials. Alternatively, the guide can comprise a plurality of discrete sections and means for securing such sections to each other. For example, the guide can be made of a plurality of shell-shaped or trough-shaped or otherwise configurated sections (such as two sections which are mirror images of each other), and the means for securing the plural sections to each other can comprise one or more threaded fasteners and/or other suitable fastener means. For example, in addition to or in lieu of being secured to each other by one or more threaded and/or other fasteners, the sections can be bonded (such as glued or soldered or welded) to each other.
If the guide comprises at least two sections, it is also possible to employ securing means which comprises at least one male coupling element provided on one of the sections and at least one complementary female coupling element provided on the other section. For example, the at least one male coupling element can comprise a hook, and the complementary female coupling element can be provided with an opening for such hook.
Furthermore, and if the guide comprises at least two sections which can be assembled prior to receiving the at least one stretch of the chain or subsequent to placing of the sections around the at least one stretch, the guide can be provided with means for centering at least one of the sections relative to the other section or sections.
The support for the guide can be installed at that side of the at least one stretch of the chain which faces toward the axes of the rotary members. This ensures that neither the support nor the means for securing the guide to the support need take up space externally of the chain. The securing means can include at least one cylindrical member, e.g., a member constituting a tube and having a cylindrical external surface. Such tubular member can serve the additional purpose of conveying at least one flow of a suitable hydraulic fluid (such as oil or another lubricant) from a source to one or more locales of actual use, such as the hubs of the flanges forming part of the aforesaid adjustable rotary pulleys.
The holder or support for the at least one stretch can be stationary and, as already mentioned above, can be installed at that side of the at least one stretch which faces toward the axes of the rotary members.
The guide can share at least some of the linear and/or angular movements of the at least one stretch of the chain relative to the two rotary members.
The guide can be installed and dimensioned in such a way that one of its sections (such as the central or median section) surrounds the corresponding portion of the at least one stretch with a first amount of play, and that at least one of the end portions of such guide surrounds the corresponding portion(s) of the at least one stretch with a second play different from (e.g., larger than) the first play.
The guide can include or carry at least one resilient part (e.g., one or more suitable springs such as coil springs or leaf springs or the like) which is installed in stressed condition so that it can bias the adjacent portion or portions of the guide in a desired direction, e.g., against the adjacent portion of the at least one stretch of the chain.
It is further within the purview of the invention to provide one or more metallic or other plastic plates, rails and/or other types of means for reinforcing at least a portion of the guide, e.g., at least that portion of the guide which is likely to undergo extensive wear as a result of repeated (such as continuous) contact with portions (such as links and/or pintles) of the endless chain.
If the support for the guide and/or at least a portion of the guide consits (at least in part) of a plastic material, such material can be, for example, a thermosetting or a thermoplastic material. For example, the plastic material can be selected from epoxy resins, polyamide, polyethylene, polypropylene, polyvinyl chloride, polyether ketone, polyester ether ketone, polybutylene therephthalate, polycarbonate, polystyrene, polyurethane, polypropylene sulfide, polyether sulphone, polyoxymethylene, styrene and copolymerisates of the above enumerated substances.
Still further, at least a portion of the guide can consist of a reinforced plastic material, e.g., a plastic material which is reinforced with glass fibers, carbon filaments and/or in any other suitable way.
The cost of the guide can be reduced, at least slightly, by assembling the guide of two sections which are mirror images of each other and which are thereupon bonded and/or otherwise (such as mechanically) fastened to each other.
It is further possible to provide the transmission with two discrete guides, one for each of the two elongated stretches or reaches which connect the two arcuate portions of the chain to each other.
Last but not least, it is equally possible to associate the at least one elongated stretch or reach of the chain with a plurality of discrete guides each of which guides (with requisite clearance) a discrete portion of the respective stretch.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved transmission itself, however, both as to its construction and the modes of assembling, installing and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.